The invention relates to a needle covering mechanism for a hypodermic syringe comprising a barrel for an injectant and a plunger for expelling the injectant from the barrel, the needle covering mechanism comprises a protective cover sleeve which is movable between a retracted position in which a needle is exposed and an extended position in which the needle is covered, a helical compression spring located inside the cover sleeve for biasing the cover sleeve towards the extended position, a lock for keeping the cover sleeve in the retracted position, and a release mechanism for releasing the lock.
The invention also relates to a needle holder for a hypodermic syringe, which needle holder comprises a needle covering mechanism
The invention further relates to a hypodermic syringe comprising a barrel and a plunger, which syringe comprises a needle covering mechanism.
Needles of used syringes constitute a risk, both by themselves and as a source to contagion. Re-use of syringes constitutes a particular risk for contagion.
Most syringes are disposable syringes with a standardised fitting which can mate corresponding standardised fittings of syringe needles. This standardised fitting enables a wide range of combinations of various syringe sizes and needle sizes. A common standardised fitting is the Luer fitting.
Various safety syringes, in which the needle is retracted or covered after use are known.
U.S. Pat. No. 5,122,118 describes an automatic needle retracting syringe in which a gelatine capsule retains a helical spring. Upon contact with the liquid injectant, the gelatine capsule weakens and allows the spring to retract the needle into the body of the syringe.
U.S. Pat. No. 5,049,133 describes a manual needle retracting syringe in which a spring which can retract the needle into the body of the syringe is releasable by moving the plunger to trigger a plurality of teeth-shaped hinges.
U.S. Pat. No. 5,188,614 describes a protective casing for use with a hypodermic syringe. A dual component foaming agent is disposed in the casing. When the components are mixed together they form an expanding and hardening plastic foam. Upon pressing the syringe into the casing subsequent to the ejection of fluid from the syringe, the foaming agents are activated and the expanding foam forces the syringe and syringe needle rearwardly within the casing, and encapsulates the used needle within the casing and foam.
U.S. Pat. No. 5,411,487 describes a needle covering mechanism for a hypodermic syringe comprising a barrel for an injectant and a plunger for expelling the injectant from the barrel, the needle covering mechanism comprises a protective cover sleeve which is movable between a retracted position in which the needle is exposed and an extended position in which the needle is covered, a helical compression spring located inside the cover sleeve for biasing the cover sleeve towards the extended position, a lock for keeping the cover sleeve in the retracted position, and a manual release mechanism for releasing the lock.
WO-A-9 205 818 describes a needle retracting syringe in which a spring which forces the needle into the plunger is released by pressing the plunger into the barrel after use.
WO 98/30261 describes a needle holder for use in combination with a syringe and a needle. The needle holder is provided with an expandable element and retention means for the expandable element. Contact between the expandable element and an injectant causes the expandable element to expand and retract the needle into the needle holder.
Prior art automatic safety syringes which function by a response to the injectant, i.e. essentially water, are generally encumbered with an unreliable and unpredictable release of the actuator.
Prior art manual safety syringes arm generally encumbered with the drawback that the force which is required to release the actuator is so large that using the safety syringe is felt cumbersome.
In some of the above mentioned safety syringes the needle and the protection mechanism are integrated in the syringe barrel. There is therefore no possibility of combining variable syringe sizes with various needle sizes, which means that a greater number of syringe variants must be held in stock to satisfy all needs. Logistically this is a big problem.
A favourable material which respond to the injectant is alginate, which loses its mechanical strength and eventually dissolves in water. Alginate items are formed by extrusion or moulding. The resulting items are however fragile and mechanically weak, and may deform when subjected to forces for a long period, which means that they easily deform or break. From this point of view, alginate is therefore not a preferable material.
NO 19996459 describes an automatic needle retracting mechanism for a hypodermic syringe comprising a body which slidingly supports a needle. A retainer for an actuator and the needle is kept in a retaining position by a spacer, preferably made from alginate, which after some time in contact with an injectant loses its mechanical strength. A filing of the needle with an injectant causes a deformation of the spacer, a release of the actuator and a retracting of the retainer and needle into a needle retraction chamber. The needle retracting mechanism may also include an inner sleeve which is manually movable towards the retainer for a manual release of the actuator. The needle retracting mechanism may be included in a needle holder or be integrated in a syringe.
In the automatic needle retracting mechanism of NO 19996459, many of the above problems are solved. The automatic needle retracting mechanism of NO 19996459 is however encumbered with the drawback that the dead volume, which contains injectant residues after the injection, is big.
The object of the invention is to provide an improved safety syringe in which the above problems are reduced or eliminated. Another object is to provide a safety syringe with both an automatic and a manual release. A further object is to provide an automatic safety syringe in which alginate is suitable as material in the injectant responding item.
The objects are achieved by a needle covering mechanism, a needle holder and a hypodermic syringe according to the preamble, which are characterized by the features of the claims.
In a first aspect the invention thus relates to a needle covering mechanism for a hypodermic syringe comprising a barrel for an injectant and a plunger for expelling the injectant from the barrel. The needle covering mechanism comprises a protective cover sleeve which is movable between a retracted position in which a needle is exposed and the syringe is operable, and an extended position in which the needle is covered and the syringe is protected. According to the invention, the protective sleeve is kept in the retracted position by a lock which is automatically releasable by contact with the injectant. Preferably the lock is also manually releasable by pushing the plunger into the bottom of the barrel.
In a second aspect the invention relates to a needle holder which is adapted to match an outlet from a hypodermic syringe, and which comprises the needle covering mechanism according to the invention. This needle holder may be used for injections or to withdraw bodily fluids, fitted to a hypodermic syringe, or fitted to another purpose designed apparatus.
In a third aspect the invention relates to a hypodermic syringe comprising a plunger and a barrel, in which the needle covering mechanism according to the invention forms an integral extension.